The use of Global Positioning Satellite (GPS) receiver is widespread for determining a position fix based upon the receipt of GPS signals from GPS satellites. One of the foremost interesting specifications of a GPS receiver is the time it takes for the receiver to acquire satellite signals and deliver position coordinates to the user after power is applied to the unit. The time required to accomplish these steps is known as the time-to-first-fix (TTFF). The TTFF of any receiver is influenced by its own unique hardware and software design, and is one of the key parameters that users of GPS receiver technology scrutinize in making purchase decisions whereby the unit with the shortest TTFF has a key advantage.
In battery powered hand held GPS receivers, for example, the acquisition time influences total battery life as the unit must be powered on continuously while the user waits for position coordinates. A short period of time between power on and first fix gives the user the data he is interested in and consumes less total energy than a unit that accomplishes the same task in a longer period of time. In addition, when one is waiting for the first fix, even short periods of time can seem like an eternity.
In automotive applications, a car, having a GPS receiver installed therein, may move and change location during the TTFF period, and thus, the uncertainty in position may be particularly dangerous if the position coordinates are intended to be used in an emergency, such as a system to identify the location of an accident since the user has no knowledge of position until after the TTFF period expires.
Hence, what is needed is an invention that greatly shortens the average TTFF in order to and make the TTFF interval as short as possible and to extend battery life.